This invention relates generally to the field of overhead insulated doors and, more specifically, to an insulated overhead door that is designed to roll open and closed in tracks.
In the cold storage distribution industry, insulated doors of various types are used to cover openings between cold areas and warm areas. Depending upon the locations and use of the opening, the doors may be opened multiple times each day, which can result in increased energy costs for maintaining desired temperatures of cold storage containers. Over time, the industry has developed and used doors with increasing insulating qualities (R-value) and with door opening assistance mechanisms (springs and counter weights) that allow for the door to be quickly opened and closed. The speed with which a door can be opened and closed is important as the more that the door can be kept closed, the more energy is saved from having to cool the cold side of the door, and the better the condition of the material that is being kept cool.
With regard to refrigerated trucks, most outer doors that are used for loading and unloading the interior truck space are made of a series of hinged horizontal metal panels filled with insulating foam material. These sections are hinged together to form a single flexible door unit that is sized to fit the opening to be covered. This single unit with several hinged sections is designed to slide up and down in tracks, with the hinged sections allowing the door to bend such that it can slide up and around a curved track path and be suspended in the tracks directly overhead from the refrigerated interior of the truck.
The current state of insulated overhead truck doors is such that they are heavy (e.g., 500+ lbs.), have a lower R-value than that desired by the shippers, and can require large numbers of hinges and other hardware for their construction. There can be significant costs associated with the regular servicing and maintenance of the hinge hardware. In addition to these drawbacks, because the current doors are made up of several separate panels held together by hinges, painting the truck door or applying the company logos or other advertisements to the back panel of the door can be complicated and expensive due, in part, to the need to align the message across multiple panels so as to be readable when door is in the closed position. If a single panel of the door is damaged and requires replacement, the entire door may need to be cleaned and repainted. Further, the doors often employ complicated gaskets in an attempt to provide an improved seal between each of the panel sections. Even then, the multiple horizontal panel design reduces the thermal performance of the entire door.
Due to the heavy nature of most existing overhead doors, large assistance springs or counter weights are often fitted to the door to enable a driver to open and close the door. The springs and/or counter weights increase the total cost and complicate installation of the doors on the truck. In addition, due to the weight of the door, automated systems for opening and closing these doors have not been commercially successful because they are generally considered to be too slow to be useful.